Plug contactor



April 9, 1963 w. s. WATTS PLUG CONTACTOR Filed May 13, 1960 INVENTOR. Uuuan Swans 3,085,222 PLUG CUNTAC'IGR William S. Watts, Harrisburg, Pa, assignor to AMP Incorporated, Harrisburg, Pa. Filed May 13, 1950, Ser. No. 28,?17 i Claims. (ill. 339-217) This invention relates to plug contactors for use with the plugboar-d or circuit connecting panel of an electrical calculating or accounting machine or the like, and more particularly to a spring detent system securing the plug from being pushed from the plugboard by ordinary pressures on the nose of the plug, but permitting Withdrawal from the plugboard by a pull on the rear portions of the lu "l he detent systems of the prior plugs of the type described are of complex design, generally including multiple parts which are expensive in manufacture and to incorporate in assembly in the plug body. It is among the objects of the present invention to provide a spring detent system for such a plug embodied in a single piece of inexpensive material and simple design, which piece may easily and quickly be assembled in a plug body. Another object of the invention is the provision of a plug of the type described which is simple and economical in construction while being rugged in use and foolproof in operation.

Other objects and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings in which there are shown and described several illustrative embodiments of the invention; it is to be understood, however, that these embodiments are not intended to be exhaustive nor limiting of the invention but are given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.

iIn the drawings:

FIGURE -1 is a longitudinal section View of an embodiment of a plug contactor incorporating features of the present invention, the plug being fully inserted in a plugboard;

FIGURE 2 is a fragmentary longitudinal section view of the plug of FIGURE 1 illustrating the action of the spring detent system during insertion of the plug in a plugboard aperture;

FIGURE 3 is a view similar to FIGURE 2 in a further stage during insertion of the plug;

FIGURE 4 is an enlarged sectional view taken along line 4-4 of FIGURE 1;

FIGURE 5 is an enlarged sectional view taken along line 55 of FIGURE 1; and

FIGURE 6 is a view similar to FIGURE 1 illustrating a modified form of a plug contactor.

The particular type of plug contactor to which this invention relates is especially adapted for use in the plugboard wiring system of an electrical accounting or calculating machine or the like, which system typically includes a fixed plugboard carrying a set of permanent contacts arranged in rows and columns. A movable plugboard removably carrying a corresponding set of plug contactors is arranged to bring the sets of contact elements into engagement so as to complete the electrical circuits desired.

Referring now to FIGURES 1 through 5, a plurality of apertures 2 of plugboard 4 receives a set of plug contactors, such as the plug generally designated at 6, in an array each for interengaging at its projecting nose 8 a 3,d85,ZZZ {Patented Apr. 9, 1963 corresponding contact in the contact set of the fixed plugboard, not shown.

Plug 6 comprises a hollow cylindrical sleeve or shell 10 of a conductive metal, such as tin-plated brass, preferably rolled up from flat sheet stock into tubular form with a butt seam 12 extending longitudinally of the sleeve, FIGURE 4. At its rearward end, the left-hand end as viewed in FIGURE 1, sleeve 10 is provided with integral means 14 by which conductor 16 is mechanically and electrically attached to the plug. Preferably attaching means 14 is formed into a ferrule from an initially U-shaped cross-sectional configuration, the ferrule being tightly crimped around wire core 18 of the conductor, FIGURE 5, by cold-forging techniques conventional in the art as illustrated, for example in Patent No. 2,600,012, issued June 10, 1952, to James C. Macy. To take up any metal of the ferrule in excess of that required to encompass wire core 18, and to align the wire core more nearly coincident with the plug axis, the anvil die, not shown, utilized in forming the crimp may have a central rib to form a longitudinally extending indentation 19 in the bottom of the crimp.

An insulating sheath 20 of a suitable resin, such as polyvinyl chloride, preferably is molded around the rear end of the plug and adjacent portions of the insulation of conductor 16. Sheath Z0 insulates the ferrule or attaching means 14 and supports the adjacent portion of conductor 16 to increase its resistance to bending fatigue while conveniently sewing as a handle for manipulating the plug.

At the rearward end of the cylindrical body of sleeve 10 adjacent the forward end of sheath 20, an integral circumferential bead 22 is provided, the bead being disposed so as to engage the face of plugboard 4 adjacent edge portions of an aperture 2 to act as a stop for limiting movement of the plug into the plugboard.

Forwardly, nose 8 smoothly converges to present a rounded tip, except for an opening-or slot 24 at the very tip, in alignment with and symmetrical about the longitudinal axis of the plug for purposes to be explained.

Disposed within sleeve 10 to provide the spring detent system of the plug is a spring 26 which is arranged to render the plug capable of being relatively easily insorted and withdrawn by sheath 20 or conductor 16, but ordinarily incapable of being dislodged from the plugboard by forces applied to the nose of the plug, except under very violent conditions where it may be preferred to lose the detent latch rather than risk extensive damage to the plug or plugboard. In general, spring 26 may be formed of any spring material of any suitable crosssectional configuration which is resistant to crumpling on axial loading, for example, steel piano wire.

As shown in FIGURE 1, the forward portion of spring 26 is generally U-shaped, the bight 28 extending into slot 24 and presenting a rounded tip, from which the legs 30 of the U gradually diverge to merge smoothly into the forward legs 32 of the V-shaped ear or detent portions 34. A pair of diametrically spaced longitudinal slots 36 in the forward portion of sleeve 10, and spaced from bead 22 a distance slightly greater than the plugboard thickness, provide openings through which detents 34 project for engaging behind the aperture edges on the front face as bead 22 comes into abutment with the rear face of the plugboard.

The rear legs 33 of detents 34 extend at a steep angle to the longitudinal axis of the plug to lie substantially parallel to the face of the plugboard on insertion of the plug. Adjacent its ends, which reenter sleeve 10, legs 38 engage the back edge of slots 36, legs 32 engaging the forward edge of slots 36 to define the rest position of the detent spring, at which position bight 28 at least is disposed within and preferably protrudes slightly out of slot 24.

On assembling the plug, spring 26 is inserted through the rear of sleeve until detents 3-4 protrude through slots 36 as bight 28 enters slot 24, legs 30 being formed with an initial bias tending to open spring 26 slightly more than the diameter of sleeve 10 to assure protrusion of detents 34 and retention of the spring in position. Slot 24, in length, is in alignment with slots 36 and thus can serve to locate detents 34 in slots 36 upon the plane of bight 28 properly oriented for insertion in slot 24. Ferrule means 14, upon wire core 18 being laid therein, is crimped and sheath 20 molded over the crimp as desired.

As thus constructed and assembled, on insertion of the plug the sloping forward legs 32 of detents 34 engage the edges of aperture 2, FIGURE 2, to initiate a camming action tending to compress the U of the detent spring, ultimately resulting in the detents being fully depressed, FIGURE 3. As bead 22 engages the rear plugboard face, slots 36 pass out of aperture 2 permitting detents 34 to spring out of sleeve 10, FIGURE 1, whereupon legs 38 are positioned along the front face of the plugboard thereby latching the plug.

To withdraw the plug it is necessary only to pull rearwardly on cord 16 or sheath 20 which applies, through the rearward movement of the forward edge of slot 36 relative to and along the sloping forward leg 32, a camming-in force component to depress detents 34. As the forward edge of slot 36 rides up leg 32 of the detent, it will be observed that, as a coincident effect, bight 28 must move relatively forwardly in sleeve 10 thus to protrude out of the nose of the plug more fully for a purpose to be explained.

It will be appreciated that by varying the slope relative to the plug axis of legs 32, the force required to insert the plug may be varied slightly; and that the force required to withdraw the plug relative to the insertion force may be varied by inclining leg portions 38 more or less from perpendicular relation relative to the plug axis.

When any attempt is made to unseat the plug by pressure applied to the nose, the effect is simply to urge detents 34 more forcefully into latching engagement with the plugboard. This effect is achieved because, in order for detents 34 to be depressed, it is necessary that, short of complete internal collapse of the spring, bight 28 must move outwardly of slot 24, as has been explained, which is contrary to the direction the applied force is urging it. Moreover, any force applied to bight 28 is directly transmitted along legs 30 to jam lateral legs 38 more tightly against the plugboar-d face, from which it can be seen that substantial resistance to dislodgment of the plug will be ofiered even where the inside ends of the spring are not anchored to the plug sleeve.

From the foregoing, it will be appreciated that bight 28 need not protrude in the rest position of spring 26 from nose 8 as shown, but may be flush to the same effect. In addition, if it be assured that at least initially the edges of the plugboard aperture exert no inward camming component on the detents, as by arranging lateral legs 38 to lie parallel to the plugboard face, or to have a slight reverse inclination, adequate strength of spring 26 assures destruction of the plug or the plugboard before the plug will unseat on pressure applied to the plug nose. Under certain conditions of use, however, it may be desirable that the plug be released prior to its destruction, in which event lateral legs 38 may be slightly inclined to the plug axis as desired. i

From the foregoing, it will be seen that the embodiments of the invention described in detail are comprised of a minimum number of parts which may be easily and quickly assembled in achievement of the objectives aforesaid. Other embodiments, of course, will occur to those skilled in the art. For example in the embodiment of FIGURE 6, to achieve simplicity in fabrication and handling, spring 26a advantageously is shown to be a sheet metal stamping. The characteristics and configuration of the plug and spring detent system otherwise are generally the same as that of the embodiment of FIGURE 1.

I claim:

1. In a plug contactor, a sleeve having a round front portion with an elongated axially symmetrical rectangular slot in the end thereof, a generally U-shaped detent spring disposed in said sleeve, the bight of the U extending into said slot and having substantially matching dimensions therewith so as to be restrained from movement laterally of the plug axis, the legs of the U having adjacent their ends detent portions biased to protrude through opposed slots in the sidewall of said sleeve, the longitudinal axes of the symmetrical slot and the opposed slots lying in the same plane.

- 2. A plug contactor according to claim 1 wherein said detent spring is formed from steel wire.

3. A plug contactor according to claim 1 wherein said detent spring is an integral sheet metal stamping.

4. A plug connector according to claim 1 wherein said detent portions are V shaped and define the extreme ends of the legs of the U.

References Cited in the file of this patent UNITED STATES PATENTS 2,490,632 Andersson et a1. Dec. 6, 1949 2,748,367 Schelke et a1. May 29, 1956 2,758,290 Watts Aug. 7, 1956 2,787,771 lFrancis Apr. 2, 1957 

1. IN A PLUG CONTACTOR, A SLEEVE HAVING A ROUND FRONT PORTION WITH AN ELONGATED AXIALLY SYMMETRICAL RECTANGULAR SLOT IN THE END THEREOF, A GENERALLY U-SHAPED DETENT SPRING DISPOSED IN SAID SLEEVE, THE BIGHT OF THE U EXTENDING INTO SAID SLOT AND HAVING SUBSTANTIALLY MATCHING DIMENSIONS THEREWITH SO AS TO BE RESTRAINED FROM MOVEMENT LATERALLY OF THE PLUG AXIS, THE LEGS OF THE U HAVING ADJACENT THEIR ENDS DETENT PORTIONS BIASED TO PROTRUDE THROUGH OPPOSED SLOTS IN THE SIDEWALL OF SAID SLEEVE, THE LONGITUDINAL AXES OF THE SYMMETRICAL SLOT AND THE OPPOSED SLOTS LYING IN THE SAME PLANE. 